I Still have this problem and no solution.
I have a Presario 7470. The computer starts fine (though slowly) and runs for a while. Then the monitor goes blank and the power light on the monitor turns yellow. The power status light on the front of the computer turns amber. When the power switch on the front of the monitor is pressed the switch itself turns green and the message "No Signal Input " is present. The computer is running normally i.e the hard drive activity light is green, fan is running etc. If I shut the computer down using the power switch on the front of the unit then the computer restarts normally and the whole problem reappears later.
thanks for all the help.